Antioxidant activities, total phenolics and HPLC analyses of the phenolic compounds of extracts from common Mediterranean plants

In this study, the total phenolic amounts and antioxidant activities of plant extracts obtained from some common Mediterranean plant species collected from different places in Jordan were determined. The phenolic constituents of these extracts were also determined using HPLC. The total phenolic amounts ranged from 52.8 to 876.9 mg GAE per 100 g dry material. The antioxidant activities were evaluated according to the 2,2-diphenyl-1-picrylhydrazyl radical scavenger method. Sage (Salvia officinalis) showed the highest antioxidant activity (91%), while the lowest (11.3%) was seen in parsley (Petroselinum crispum). A strong correlation (r = 0.85) between antioxidant activity and total phenolic content was found. The phenolic compounds identified by HPLC were gallic acid, protocatechuic acid, catechin, gentisic acid, chlorogenic acid, vanillic acid, syringic acid, caffeic acid, epicatechin and benzoic acid. All the investigated plants contain gallic acid, whose phenolic content ranged from 0.4 to 37.8 mg per 100 g, catechin (0.3-339.9 mg per 100 g), protocatechuic acid (0.3-41.9 mg per 100 g) and gentisic acid (0.3-35.8 mg per 100 g), while caffeic acid (0.3-2.6 mg per 100 g) was detected in six species only. These natural plant phenolics could thus be a good source of antioxidants for applications in food.     

Essential oil constituents,phenolic content and antioxidant activity of Lavandula stricta Delile growing wild in southern Iran

Lavandula stricta belongs to the Lamiaceae family and is considered as an endemic medicinal plant in southern Iran. Essential oil composition, total phenolic content and antioxidant activity from two different populations of L. stricta were studied for the first time. A GC and GC/MS analysis of essential oil isolated from the aerial part of L. stricta identified 31 constituents; the major constituents were α-pinene (58.34–63.52%), linalool (8.85–9.36%), 3-methyl butyl 2-methyl butanoate (7.45–7.70%), sabinene (2.84–3.56%), limonene (2.87–3.21%) and myrcene (2.25%). The total phenolic content of methanolic extracts was determined with the Folin–Ciocalteu reagent and the antioxidant activity of methanolic extract and essential oil were determined with the 2, 2-diphenyl-1-picryl hydrazyl free radical scavenging assay, respectively. Total phenols varied from 61.05 to 64.45 mg GAE/g dry weight, and IC₅₀ values in the radical scavenging assay ranged from 334.11 to 395.23 μg/mL in methanolic extracts and 420–475 μg/mL in essential oil.     

Antioxidant potential of non-oil seed legumes of Indonesian’s ethnobotanical extracts

This study investigated the in vitro antioxidant properties (DPPH, ABTS, CUPRAC and FRAP), total phenolic content and flavonoid content of extracts from three non-oil seed legumes (Phaseolus lunatus red and white, and Canavalia ensiformis), local edible seeds from Indonesia, obtained using different solvent system (distilled water, 70% ethanol, and 100% ethanol). The variety of legume was a major source of variation in the phenolic contents, flavonoid content and antioxidant activity. HPLC analysis of the non-oil seed legume extracts identified gallic acid, epicatechin and coumaric acid. Among the varieties of non-oil seed legume extracts, the phenolic content varied from 15.21–38.60 mg gallic acid equivalents/g dry weight and the flavonoid content was 11.73–24.61 mg catechin equivalents/g dry weight. The antioxidant activity of the extracts suppressed the reactive oxygen species (ROS) generation and cellular damage induced by UV-B in HaCaT cells. These results showed that antioxidant activity (1.83–19.42% of inhibition DPPH; 2.99–37.29% of inhibition ABTS; 0.20–2.47 µM CUPRAC value; and 0.96–1.10 µM of FRAP value) of extracts possessed strong radical scavenging activity as well as inhibited ROS generation in a dose-dependent manner without showing any cytotoxicity. Collectively, the data presented that antioxidant of the extracts have potent antioxidant activity and decreasing ROS generation in HaCaT cells. It can be intimately used as alternative criterion for antioxidant and antiradical activities that can be utilized as a functional food and nutraceutical ingredients.     

HPLC profiling of phenolics and flavonoids of Adonidia merrillii fruits and their antioxidant and cytotoxic properties

In this study the antioxidant and cytotoxicity activity of the Adonidia merrillii fruits were investigated using different solvent polarities (methanol, ethyl acetate and water). The results showed that the total phenolic and flavonoid contents of the methanolic extract was higher compare with other extract with respective values of 17.80 ± 0.45 mg gallic acid equivalents/g dry weight (DW) and 5.43 ± 0.33 mg rutin equivalents/g DW. Beside that The RP-HPLC analyses indicated the presence of gallic acid, pyrogallol, caffeic acid, vanillic acid, syringic acid, naringin and rutin. In the DPPH, NO2 and ABTS scavenging assays, the methanolic extract exhibited higher antioxidant activity as compared to the ethyl acetate and water extracts. The extracts exhibited moderate to weak cytotoxic activity in the assays using human hepatocytes (Chang liver cells) and NIH/3T3 (fibroblasts cell) cell lines. The findings showed the Adonidia merrillii fruit extracts to possess considerable antioxidant and cytotoxicity properties. The fruit, therefore, is a potential candidate for further work to discover antioxidant and cytotoxic drugs from natural sources.     

Chemical composition and antioxidant activity of Borago officinalis L. leaf extract growing in Algeria

The aqueous and hydroalcoholic extracts of borage (Borago officinalis) leaves from Annaba region (Algeria) were preliminary analyzed for their phenolic profile (total phenolics, total flavonoids, total flavonols, total tannins and total anthocyanins). These extracts were evaluated for their antioxidant properties by different methods such as DPPH radical scavenging, test NBT and total antioxidant activity. The two extracts have exhibited a high antiradical capacity. Indeed, the ethanolic extract showed the lower IC50 values and the highest amount of phenolics (94.09 ± 1.72 mg gallic acid/g dry extract). Using LC-MS/MS analysis, it was possible to identify phenolic acids, flavonoids, sterol and for the first time oleuropein was identified in the aqueous extract of the plant. The obtained results have demonstrated that phenolic compounds are the major contributor to the antioxidant activity of plants.     

Seasonal variation in total phenolic and flavonoid contents and DPPH scavenging activity of Bellis perennis L. flowers

Variations in total phenolic and flavonoid contents as well as antioxidant activity of Bellis perennis (common daisy) flowers were investigated. The flowers were collected monthly (from March to October, i.e., during the usual flowering season of the plant) at three localities in three different years. Total flavonoids were determined spectrophotometrically by two methods: by formation of a complex with aluminium chloride after acidic hydrolysis of flower extracts (method 1) and by reaction with boric and oxalic acids in extracts without their modification (method 2). Total phenolics were determined spectrophotometrically using the Folin-Ciocalteu reagent. The antioxidant activity was determined spectrophotometrically by a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The contents of flavonoids varied from 0.31 to 0.44 mg quercetin equivalent/100 mg dry weight (method 1) and from 1.37 to 2.20 mg pigenin-7-glucoside equivalent/100 mg dry weight (method 2). Total phenolics ranged from 2.81 to 3.57 mg gallic acid equivalent/100 mg dry weight. The antioxidant activity expressed as IC(50) values varied from 66.03 to 89.27 μg/mL; it is about 50, 30, 20, and 10 times lower as compared with quercetin, ascorbic acid, Trolox?, and butylhydroxytoluene, respectively, and about five times higher in comparison with apigenin-7-glucoside. There is a significant correlation between antioxidant activity and total phenolics. No correlation between total flavonoid contents and antioxidant activity was observed. Contents of phenolics and flavonoids as well as antioxidant activity of daisy flowers vary to a relatively small extent during the year and are not dependant on the time of collection. Thus, the flowers possess comparable quality as to these characteristics over the whole flowering season of Bellis perennis. Effects of environmental factors on the amounts of secondary metabolites in plants are also discussed.     

Effect of extraction conditions on measured total polyphenol contents and antioxidant and antibacterial activities of black tea

Black tea was extracted for 2, 8 and 18 h with absolute acetone, N,N-dimethyl-formamide (DMF), ethanol and methanol and their 50% aqueous solutions. The extracts were screened for total polyphenol contents, antioxidant and antibacterial activities. The polyphenol content of the extracts was found to be in the range of 0.44-114.01 mg gallic acid equivalents (GAE)/g dry weight tea, depending on the solvent used and the length of the extraction process. In general, aqueous acetone or DMF extracts displayed the highest polyphenol contents and antioxidant activity, while absolute acetone was the least efficient solvent. Antioxidant activities of tea extracts tested using the reducing power and 2,2-diphenyl-1-picryhydrazyl (DPPH) radical methods ranged from 0.09 to 1.18 and from 2.60 to 95.42 %, respectively, depending on the extraction conditions and the antioxidant activities correlated well with the polyphenol concentrations. Aqueous solvent black tea extracts also possessed antibacterial activity, depending on the solvent used and bacterial species tested. Staphylococcus aureus was found to be the most sensitive to all tea extracts, except for the methanol extract. Tea extracts were not effective against Y. enterocolitica, L. monocytogenes and E. coli O157:H7.     

Untargeted Phytochemical Profile,Antioxidant Capacity and Enzyme Inhibitory Activity of Cultivated and Wild Lupin Seeds from Tunisia

Lupin seeds can represent a valuable source of phenolics and other antioxidant compounds. In this work, a comprehensive analysis of the phytochemical profile was performed on seeds from three Lupinus species, including one cultivar (Lupinus albus) and two wild accessions (Lupinus cossentinii and Lupinus luteus), collected from the northern region of Tunisia. Untargeted metabolomic profiling allowed to identify 249 compounds, with a great abundance of phenolics and alkaloids. In this regard, the species L. cossentinii showed the highest phenolic content, being 6.54 mg/g DW, followed by L. luteus (1.60 mg/g DW) and L. albus (1.14 mg/g DW). The in vitro antioxidant capacity measured by the ABTS assay on seed extracts ranged from 4.67 to 17.58 mg trolox equivalents (TE)/g, recording the highest values for L. albus and the lowest for L. luteus. The DPPH radical scavenging activity ranged from 0.39 to 3.50 mg TE/g. FRAP values varied between 4.11 and 5.75 mg TE/g. CUPRAC values for lupin seeds ranged from 7.20 to 8.95 mg TE/g, recording the highest for L. cossentinii. The results of phosphomolybdenum assay and metal chelation showed similarity between the three species of Lupinus. The acetylcholinesterase (AChE) inhibition activity was detected in each methanolic extract analyzed with similar results. Regarding the butyrylcholinesterase (BChE) enzyme, it was weakly inhibited by the Lupinus extracts; in particular, the highest activity values were recorded for L. albus (1.74 mg GALAE/g). Overall, our results showed that L. cossentinii was the most abundant source of polyphenols, consisting mainly in tyrosol equivalents (5.82 mg/g DW). Finally, significant correlations were outlined between the phenolic compounds and the in vitro biological activity measured, particularly when considering flavones, phenolic acids and lower-molecular-weight phenolics.     

Antioxidant capacity and phenolic content of Caesalpinia pyramidalis Tul. and Sapium glandulosum (L.) Morong from Northeastern Brazil

The aims of this study were to quantify the phenolic content and evaluate the antioxidant potential of extracts from the bark and leaves of C. pyramidalis and S. glandulosum. The total phenolic content (TPC) and total tannin content (TTC) were determined using the Folin-Ciocalteu method, and the total flavonoids content (TFC) was measured via complexation with aluminum chloride. The antioxidant activity was evaluated with DPPH (2.2-diphenyl-1-picrylhydrazyl) and FIC (ferrous ion chelating) assays. The TPC ranged between 135.55 ± 9.85 and 459.79 ± 11.65 tannic acid equivalents (TAE) in mg/g material (mg TAE/g). The leaves of both species contained high levels of tannins and flavonoids. The crude ethanol extracts (CEE) from the bark of C. pyramidalis showed high antioxidant activity when compared to ascorbic acid and rutin, whereas the CEE from the leaves was more efficient in chelating ferrous ions. C. pyramidalis had very high phenolic content and anti-radical activity, which indicates a need for further studies aimed at the purification and identification of compounds responsible for the antioxidant activity.     

Antioxidant activity of lignin phenolic compounds extracted from kraft and sulphite black liquors

The antioxidant activity of the phenolic compounds present in industrial black liquors obtained from the two cooking processes (kraft and sulphite) used in Portugal to produce Eucalyptus globulus pulp was evaluated. The black liquors treated at several pH values were extracted with ethyl acetate. Phenolic fractions were further separated by liquid chromatography of the crude extracts of kraft liquor at pH = 6 and sulphite liquor at the original pH. Total phenolic content was determined in terms of gallic acid equivalents (Folin-Ciocalteu colorimetric method), and the antioxidant activity in the crude extracts at several pH values and in the separated fractions was measured using the DPPH test for radical scavenging capacity. The total phenolic content of crude extracts and separated fractions ranged from 92.7 to 181.6 and from 91.6 to 1,099.6 mg GAE/g, respectively, while the antioxidant activity index (AAI) ranged from 2.20 to 3.41 and from 2.21 to 11.47 respectively, showing very strong antioxidant activity in all studied cases. The fractions separated by column chromatography were submitted to mass spectrometry analysis and the results were compared to others in the literature of natural products, mainly from Eucalyptus, and the characteristic bands of functional groups were identified by 1H-NMR and FTIR. These methods allowed the identification of 17 phenolic compounds.     

Assessment of the content of phenolics and antioxidant action of inflorescences and leaves of selected species from the genus Sorbus sensu stricto

In order to find new sources of natural antioxidants, the antioxidant potential of 70% methanolic extracts from the inflorescences and leaves of 16 species from the genus Sorbus s.s. was evaluated using two complementary in vitro test systems: the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging assay and the AAPH [2,2￠-azobis-(2-amidinopropane)dihydrochloride]-induced linoleic acid (LA) peroxidation test. The radical-scavenging capacities of the extracts towards the DPPH radical were in the range of 0.25-0.86 millimolar Trolox? equivalents/g dry weight. They were significantly correlated (r=-0.8089, p<0.001) with the results of the LA-peroxidation test, indicating the Sorbus extracts to be universal antioxidants. Significant linear correlations were also found between the different antioxidant potentials and total phenolic contents as estimated by the Folin-Ciocalteu method and further verified by serial determinations of proanthocyanidins, chlorogenic acid isomers and flavonoids (?rêin the range of 0.71-0.95, p<0.001). Cluster analysis of the data matrix identified the ten samples (inflorescences of S. aucuparia, S. pohuashanensis, S. decora, S. koehneana, S. commixta, S. gracilis, and S. sitchensis, and the leaves of S. wilfordii, S. pogonopetala, and S. gracilis) exhibiting the highest antioxidant activity and total phenolic levels and therefore the greatest potential as effective sources for natural health products.     

Dietary burden of phenolics per serving of "Mountain tea" (Sideritis) from Macedonia and correlation to antioxidant activity

This work was afforded from 2 points of view, phytochemical evaluation and relation to antioxidant activity and dietary burden of phenolics of a cup of "Mountain tea", a drink obtained by domestic infusion of Sideritis. Phytochemically, two extraction protocols using water and methanol as solvent were used for comparison. Methanol and boiling water extracts (by domestic infusion procedure) showed that extracts were rich in bound forms of phenolics such as hydroxycinnamic acids, phenylethanoid glycosides and flavonoid glycosides. The total phenolic content for Sideritis species ranged around 190 mg per serving (2 g infusion bag) for methanol extracts and around 72 mg per serving in water extracts. Among the two different Macedonian Sideritis species, Sideritis raeseri (wild growing) showed the highest phenolics content in both extracts (212 mg and 89 mg per serving, respectively). Concerning the phenolic content in the different aerial parts, leaf was the richest plant organ in phenolics followed by flower and stem with the lowest amount. The methanol extract from Sideritis raeseri (wild growing) showed the highest antioxidant capacity as shown by DPPH, ABTS and FRAP assays. The antioxidant capacity was linearly correlated with phenolic content. Nutritionally, the dietary burden of phenolics of a "Mountain tea" bag for domestic infusion (serving size) was established at 89 mg for an homogeneous and equal distribution of the different aerial parts (leaf, flower and stem). However, and according to our results a rate of 60% leaf and 40% flower would increase the content of bioavailable phenolics and also the total phenolics content of a serving bag of "Mountain tea".     

Production of Verbascoside,Isoverbascoside and Phenolic Acids in Callus,Suspension, and Bioreactor Cultures of Verbena officinalis and Biological Properties of Biomass Extracts

Callus, suspension and bioreactor cultures of Verbena officinalis were established, and optimized for biomass growth and production of phenylpropanoid glycosides, phenolic acids, flavonoids and iridoids. All types of cultures were maintained on/in the Murashige and Skoog (MS) media with 1 mg/L BAP and 1 mg/L NAA. The inoculum sizes were optimized in callus and suspension cultures. Moreover, the growth of the culture in two different types of bioreactors—a balloon bioreactor (BB) and a stirred-tank bioreactor (STB) was tested. In methanolic extracts from biomass of all types of in vitro cultures the presence of the same metabolites—verbascoside, isoverbascoside, and six phenolic acids: protocatechuic, chlorogenic, vanillic, caffeic, ferulic and rosmarinic acids was confirmed and quantified by the HPLC-DAD method. In the extracts from lyophilized culture media, no metabolites were found. The main metabolites in biomass extracts were verbascoside and isoverbascoside. Their maximum amounts in g/100 g DW (dry weight) in the tested types of cultures were as follow: 7.25 and 0.61 (callus), 7.06 and 0.48 (suspension), 7.69 and 0.31 (BB), 9.18 and 0.34 (STB). The amounts of phenolic acids were many times lower, max. total content reached of 26.90, 50.72, 19.88, and 36.78 mg/100 g DW, respectively. The highest content of verbascoside and also a high content of isoverbascoside obtained in STB (stirred-tank bioreactor) were 5.3 and 7.8 times higher than in extracts from overground parts of the parent plant. In the extracts from parent plant two iridoids—verbenalin and hastatoside, were also abundant. All investigated biomass extracts and the extracts from parent plant showed the antiproliferative, antioxidant and antibacterial activities. The strongest activities were documented for the cultures maintained in STB. We propose extracts from in vitro cultured biomass of vervain, especially from STB, as a rich source of bioactive metabolites with antiproliferative, antioxidant and antibacterial properties.     

Phenolic enriched extract of Baccharis trimera presents anti-inflammatory and antioxidant activities

Baccharis trimera is a plant popularly used as a tea and to treat gastrointestinal diseases and inflammatory processes as well. The total phenolic content was determined and the antioxidant and anti-inflammatory activities of six extracts (dichloromethane, ethyl acetate, butanol, aqueous, saponin and phenolic) from B. trimera were evaluated. Using carrageenan-induced pleurisy as a model of acute inflammation, the phenolic extract at 15 mg/kg decreased significantly the analyzed parameters when compared to the carrageenan group ( p < 0.05), thus showing potential anti-inflammatory activity. The total phenolic content and antioxidant activity were evaluated by the Folin-Ciocalteau and DPPH methods, respectively. Phenolic and ethyl acetate extracts presented higher antioxidant activity ( p < 0.05) than ascorbic acid. The phenolic extract also showed the highest antioxidant potential in relation to the other extracts, thus suggesting that the antioxidant and anti-inflammatory activities were due to the presence of phenolic compounds.     

Phytochemical identification of Lithocarpus polystachyus extracts by ultra-high-performance liquid chromatography–quadrupole time-of-flight–MS and their protein tyrosine phosphatase 1B and α-glucosidase activities

Lithocarpus polystachyus leaves exhibit antidiabetic activity and is consumed as a herbal tea in China. In this study, phytochemical profiles of L. polystachyus leaves were identified and characterized by ultra-high-performance liquid chromatography–quadrupole time-of-flight–MS in both positive and negative ion modes. A total of 17 compounds were tentatively characterized and identified by accurate mass and characteristic fragment ions. The total phenolic contents in the leaf extracts ranged from 9.0 to 13.4 g gallic acid equivalents/100 g of dry weight (DW). In addition, the effect of these extracts on inhibiting the activities of α-glucosidase and protein tyrosine phosphatase 1B (PTP1B) were evaluated. L. polystachyus extracts demonstrated significant inhibition of α-glucosidase (more than 88.1% at a concentration of 1.25 mg/mL) and acarbose (93.6% at a concentration of 5 mg/mL) while the PTP1B inhibition rate was over 84.3%. The antioxidant capacities of the leaf extracts were determined using 2,2-diphenyl-1-picrylhydrazyl, ABTS, and ferric reducing ability of plasma methods and ranged from 50.5 to 72.5 g trolox, from 43.2 to 77.7 g trolox, and from 5.0 to 10.6 g butylated hydroxytoluene (BHT; equaling trolox or BHT per 100 g of DW), respectively. Based on these results, L. polystachyus can be considered as a functional food owing to its antidiabetic and antioxidative activities, which are attributed to its rich phenolic and dihydrochalcone contents.     

Essential oil composition and antioxidant activity of Stachys sylvatica L. (Lamiaceae) from different wild populations in Kosovo

Leaves and inflorescences of Stachys sylvatica L. (Lamiaceae) were collected from three different wild populations in Kosovo to study the natural variation of the chemical composition of essential oils, total flavonoids, total phenolics and the antioxidant activity. Essential oils were obtained by steam distillation and analysed by GC-FID and GC-MS, whereas total flavonoids, total phenolics and antioxidant activities were determined by spectrophotometric methods. Yields of essential oils ranged from 0.001% to 0.007% (v per dry weight). Twenty-eight volatile constituents were identified. The main constituents were α-pinene, β-pinene and germacrene-D. Total phenolics ranged from 39.3 to 70.8?mg?g?1 dry mass, whereas total flavonoid content ranged from 30.44 to 70.63?mg?g?1 dm. The antioxidant activity, as measured by the DPPH method, exhibited a rather high degree of activity ranging from 25.5% to 57.2%, whereas the FRAP antioxidant activity showed a lower variability and ranged from 93 to 133.4?mg?g?1 dm.     

Bioactive compounds, RP-HPLC analysis of phenolics, and antioxidant activity of some Portuguese shrub species extracts

In the ecosystem of Serra Da Estrela, some plant species have the potential to be used as raw material for extraction of bioactive products. The goal of this work was to determine the phenolic, flavonoid, tannin and alkaloid contents of the methanolic extracts of some shrubs (Echinospartum ibericum, Pterospartum tridentatum, Juniperus communis, Ruscus aculeatus, Rubus ulmifolius, Hakea sericea, Cytisus multiflorus, Crataegus monogyna, Erica arborea and Ipomoea acuminata), and then to correlate the phenolic compounds and flavonoids with the antioxidant activity of each extract. The Folin-Ciocalteu's method was used for the determination of total phenols, and tannins were then precipitated with polyvinylpolypyrrolidone (PVPP); a colorimetric method with aluminum chloride was used for the determination of flavonoids, and a Dragendorff's reagent method was used for total alkaloid estimation. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) and beta-carotene bleaching tests were used to assess the antioxidant activity of extracts. The identification of phenolic compounds present in extracts was performed using RP-HPLC. A positive linear correlation between antioxidant activity index and total phenolic content of methanolic extracts was observed. The RP-HPLC procedure showed that the most common compounds were ferulic and ellagic acids and quercetin. Most of the studied shrubs have significant antioxidant properties that are probably due to the existence of phenolic compounds in the extracts. It is noteworthy to emphasize that for Echinospartum ibericum, Hakea sericea and Ipomoea acuminata, to the best of our knowledge, no phytochemical studies have been undertaken nor their use in traditional medicine been described.     

Antioxidant, total phenolic content and cytotoxicity evaluation of selected Malaysian plants

Aqueous and ethanol extracts of different traditional Malaysian plants (Polygonum minus, Andrographis paniculata, Curcuma xanthorrhiza, Momordica charantia and Strobilanthes crispus) were evaluated for their antioxidant properties, total phenolic content and cytotoxic activity. Antioxidant activity was evaluated by using 1,1-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. The results showed that ethanol extracts contain high antioxidant activities compared to aqueous extracts. The findings exhibited a strong correlation between antioxidant activity and the total phenol contents. In addition, all the plant extracts showed non-toxic effects against a normal human lung fibroblast cell line (Hs888Lu). Although traditionally aqueous extracts are used, we determined that ethanol extracts usually achieved better activity in the assays.     

Profiling of phenolic compounds and antioxidant activity of dry extracts from the selected Sorbus species

The antioxidant efficiency of dry extracts from inflorescences and/or leaves of seven Sorbus species was studied using four in vitro tests of SET (single electron transfer) and HAT-type (hydrogen atom transfer) mechanisms. The 70% methanol extracts and its diethyl ether, ethyl acetate, n-butanol and water fractions were tested in parallel with the phenolic standards, e.g., caffeic acid, quercetin, BHA, BHT, and Trolox. The SET-type activity of the extracts depended primarily on the extraction solvent. The most valuable extracts were n-butanol and ethyl acetate ones, which activity was high in the DPPH (EC(50) = 3.2-5.2 μg/mL), TEAC (2.8-4.0 mmol Trolox/g), and FRAP (9.8-13.7 mmol Fe2+/g) tests, and strongly correlated with the total phenolic levels (39.6-58.2% of gallic acid equivalents). The HPLC-PDA analysis of the extracts led to the identification of chlorogenic acid, isoquercitrin, hyperoside, rutin, quercetin 3-O-sophoroside, and sexangularetin 3-O-β-D-glucopyranoside as the main components. Apart from flavonoids and hydroxycinnamic acids, proanthocyanidins have also a significant impact on the SET-type activity. The HAT-reactivity of the extracts in the linoleic acid peroxidation test (IC(50) = 36.9-228.3 μg/mL) depended more strongly on the plant tissue than on the extraction solvent, and its correlation with the phenolic content was weak. Both SET and HAT-type activity of the most potent Sorbus extracts was comparable with the activity of the standards, indicating their great potential as effective sources for health products.     

Impact of Harvest Conditions and Host Tree Species on Chemical Composition and Antioxidant Activity of Extracts from Viscum album L.

The content of plant secondary metabolites is not stable, and factors such as the region/location effect and seasonal variations have an impact on their chemical composition, especially in parasitic plants. Research in this area is an important step in the development of quality parameter standards of medicinal plants and their finished products. The effects of the time and place of harvest and the host tree species on the chemical composition and antioxidant activity of mistletoe extracts were investigated. Statistical tools were used to evaluate the results of the spectrophotometric and LC-ESI-MS/MS studies of the phenolic composition and antioxidant activity. The investigations indicate that the qualitative and quantitative composition, influencing the biological activity of mistletoe extracts, largely depends on the origin of the plant. The mistletoe extracts exhibited a rich phenol profile and high antioxidant activity. The chemometric analysis indicated that mistletoe collected from conifers (Viscum abietis and Viscum austriacum) had the most advantageous chemical composition and antioxidant activity. Moreover, the chemical profile and biological activity of the plant material were closely related to the climatic conditions and location of the harvested plant. Higher levels of phenolic compounds and high antioxidant activity were found in extracts obtained from plant material collected in cold weather with the presence of snow and less sunshine (autumn–winter period).